Across the country churches held special masses, and towns and cities commemorated the anniversary with ceremonies and vigils.

On December 13, 1981 troops and armoured vehicles poured onto Poland's streets, the country's borders were sealed and thousands of Solidarity activists arrested as the communist authorities reasserted control after facing the prospect of revolution.

Some 10,000 people were rounded up and about 100 died during martial law.

Lech Walesa, one of those arrested, condemned the declaration as a "great crime the broke the unity of the nation".

General Wojciech Jaruzelski, then Poland's leader, still claims he declared martial law to avoid a Soviet military intervention ordered by a Kremlin fearing that Solidarity might rest one of its key satellite states from its grasp.

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But, according to Nato documents declassified to coincide with the 30th-anniversary of the declaration of martial law, the Soviet Union had little intention of intervening in Poland as it had done in Czechoslovakia in 1968 and Hungary 12 years earlier.

One secret Nato report from October 1981 said the Soviet Union appeared "keen to avoid" military intervention, preferring to rely on threats instead, while one from December reported "no signs of Soviet military moves".

Jaruzelski, now 83, still faces bitterness and resentment over his role in 1981 and the anniversary of martial law has seen demonstrations outside his Warsaw home. He has also had to withstand numerous attempts to have him prosecuted for treason.

Along with formal events, in Warsaw Poland's main opposition party Law and Justice organised a demonstration not only to mark the anniversary but also to protest against closer EU integration, which Jaroslaw Kaczynski, the party's leader, has described as a new threat to Polish independence.